Prenatal Diagnosis of Congenital Adrenal Hyperplasia due to Deficiency of Steroid 21-Hydroxylase Enzyme - Experience from a Tertiary Care Center in India

Background and Objectives: Congenital adrenal hyperplasia (CAH) belongs to a group of disorders caused by the deficiency of the steroid 21-hydroxylase enzyme that impairs the production of adrenal steroids. Many at-risk families opt for prenatal diagnosis (PND) to prevent the birth of an affected child in view of increased mortality in the salt-losing severe cases, genital ambiguity in females, and precocious puberty in males. Before prenatal testing, it is imperative to know the pathogenic variant(s) in the affected child before PND is offered to the families. However, in reality, many families either do not have access to molecular testing or the proband is unavailable for testing. In this study, we report the experience at a tertiary care genetics center of PND in 139 families at risk, utilizing multiple genetic and molecular methods for testing. Materials and Methods: Most families recruited in this study had at least one clinically diagnosed child with CAH. Molecular methods like multiplex ligation probe amplification, Sanger sequencing, polyacrylamide gel electrophoresis, and linkage were used for variant identification in the proband, if available, or in the parents. Variant segregation in parents was done in each family. Maternal cell contamination was ruled out in every sample for which prenatal testing was performed. Results: A total of 139 prenatal samples were analyzed, of which 33 (23.7%) fetuses were affected and 106 (76.3%) were unaffected. Of the 106, 64 (60.4%) were heterozygous (carriers) and 42 (39.6%) were homozygous for wild-type variants. Conclusion: With different molecular methodologies performed on chorionic villus or amniotic fluid, 100% cases were correctly reported, indicating the efficacy of multiple methodologies. Linkage was useful in families where molecular workup was not done. Despite the absence of an affected child in the families, prenatal diagnostic testing could be offered after comprehensive carrier screening and determining the carrier status of the couple.